36 



BOTANY: HARRIS AND SINNOTT 



PROC. N. A. S. 



The modal number of primary double bundles in the region of transition 

 from root to stem structure at the base of the hypocotyl is four in the di-. 

 merous and six in the trimerous and hemitrimerous seedling. In the 

 normal seedlings more than four bundles may occur, but in no case have 

 fewer than this number been observed. In the trimerous seedling varia 

 tion both above and below the mode is found, the numbers ranging from 

 four to eight. On the average the number is from 1.38 to 1.89 bundles 

 higher (or from 30.5 to 47.0% higher) in the trimerous than in the 

 dimerous seedlings. 



Intercalary bundles, which are rather uncommon in seedling anatomy 

 in general, occur in from 11 to 46% of the normal seedlings, whereas they 

 are found in only 9 to 29% of the trimerous and in 28 to 43% of hemi 

 trimerous seedlings. The average number of intercalary bundles is alsc 

 generally higher in the dimerous plantlets. 



Considering the total bundle number at the base of the hypocotyl. 

 (primary bundles plus intercalary bundles) the trimerous and hemi 

 trimerous seedlings have from 0.77 to 1.91 bundles, or from 14.4 to 46.7% 

 more than the dimerous seedlings. The differentiation of the dimerous 



